Then I heard from a friend who visited Switzerland 3 weeks before my trip, he is using this Swisscom NATEL easy plan, which to me, sounds very convenient and affordable.

The moment I arrived in Geneva Airport, went to the post office to get this plan. Some details here:

Requirement: A passport (or ID document) is required to purchase.

Upfront fee: CHF20 (as credit)

Credit usage: CHF2/day, that means CHF20 is good for 10 days.

Data limit: The credit is valid for a month with 4GB limit. For me, I was there for 14 days so it's more than enough. (as per the manual, if you use over 4GB, you can still access data but speed will be much slower).

Topup: CHF10 per topup if required, good for another 5 days. Can be done online via Swisscom website

Able to make/receive calls? Yes, but I didn't try at all. Rates applicable, check the plan details

When I bought it, there was a BONUS 100MB before the actual credit usage. So I think it's great for tourist arriving on day1 to start using that 100MB, only on day2 you get the credit deducted for the first time.

The quality? Great I'd say, it is very reliable throughout my trip. I did experience some "signal lost", but really not affecting my trip at all.